1. Field of the Invention
The present invention relates to an apparatus for manufacturing a color filter, and more particularly, to an apparatus and method of manufacturing a color filter adsorbing toner nano-particles instead of paint or dye drops (hereinafter, referred to as ink) to a glass substrate by electrostatic force in order to form a color filter cell in a uniform thickness at a precise position.
2. Description of the Related Art
FIG. 1 is a diagram illustrating the use of a color filter in a general thin film transistor-liquid crystal display) TFT-LCD panel 100. In a general TFT-LCD, the TFT-LCD panel 100 is used for receiving image data and displaying a certain image to be shown to a user. The TFT-LCD panel 100 may be used in various devices for displaying a certain image, such as mobile phones, digital cameras, computer screens, and television screens.
The TFT-LCD panel 100 includes a lower plate 110 and an upper plate 120, both of which include a plurality of electrodes for forming an electric field. A crystal liquid layer is formed between the lower plate 110 and the upper plate 120. In addition, polarization plates attached to each of the lower plate 110 and the upper plate 120 may be included in order to polarize light. The brightness of light in the TFT-LCD panel 100 is controlled by applying a voltage according to gray level to a pixel electrode for rearranging liquid molecules. In the lower plate 110 of the TFT-LCD panel 100, in order to apply the gray level voltage to be applied to pixel electrodes, a plurality of switching devices such as TFTs connected to the pixel electrodes is included. In the upper plate 120 of the TFT-LCD panel 100, in order to display light of a back light in three colors, a color filter formed of cells of red (R), green (G), and blue (B) for each pixel is included. A black matrix exists between each cell of the pattern of a color filter, which blocks light passing through each of R, G, and B pixels to prevent interference with each other, absorbs external light which should not be reflected, and conceals TFTs, a gate line, and a source line.
In order to manufacture the described color filter, in general, a black matrix is formed and processes of applying color photoresist (PR), exposure, and development are performed. In the described method, since much manufacturing time is consumed and material is wasted, an inkjet printing method has been developed.
In the inkjet printing method, since a process is performed so that color filter cells of each of R, G, and B are printed via an inkjet head similar to drawing on a sheet, without a patterning process of removing PR, as shown in FIG. 2, manufacturing time may be notably reduced and material may be saved by the simplified process.
However, in the general printing method, since each cell having a size 260*70*1 μm for a resolution higher than SVGA has to be filled with ink drops for each color filter cell, jetted between black matrixes, ink overflows from those cells with a depth of less than 1 μm to adjacent cells. Also, in the inkjet printing method, ink in each color filter cell does not have a uniform thickness, as shown in FIG. 3 and a coffee ring phenomenon in which peripheral ink is thicker than the center occurs, which is caused by non-uniform solvent evaporation of the ink.
FIG. 4 is a diagram illustrating a conventional method of manufacturing a color filter by using electrostatic force. Referring to FIG. 4, in order to form a color filter cell on a glass substrate, an electric conductor, for example, metal, on which an optical conductor, for example, indium-tin-oxide (ITO), is deposited, is required. In the conventional method of using electrostatic force, in order to form an electrostatic latent image in a relevant position of the optical conductor corresponding to the color filter cell, the surface of the optical conductor is exposed in order to be electrified in a pattern meeting certain LCD resolution standard requirements. If the electrostatic latent image of the certain resolution standard requirements is formed on the surface of the optical conductor, toner having an electric charge may be adsorbed to only a latent image by electrostatic force of the electrostatic latent image. Next, in the case the optical conductor to which the toner is adsorbed is transferred to be adjacent to the glass substrate and the glass substrate is electrified to have an electric charge opposite to the toner by using an electrification unit generating corona discharge, the toner of a relevant color is separated from the optical conductor and transcribed to the glass substrate. A more detailed description is disclosed in Japanese Patent Application No. 1995-281175 filed by Casio.
However, in the conventional method of manufacturing a color filter by using electrostatic force as shown in FIG. 4, an electric conductor on which an optical conductor is deposited is additionally required in the shape of a mask and two electrification processes, which are the electrification of the surface of the optical conductor before an exposure process, and the electrification of a glass substrate for transcription, are required, thereby increasing manufacturing cost and manufacturing time.